Patent Document 1 discloses a method for detecting microorganisms contained in foods and the like. According to the detection method disclosed in this document, images of a plate for microbial detection are captured by a CCD line sensor before and after cultivation. The obtained image data are compared to count microbial colonies. Patent Document 2 discloses a method for detecting microorganisms by using color data specified in advance.
In the detection method of Patent Document 1, colonies are counted by simply comparing image data. Therefore, when relative positions between a camera and a medium are changed before and after cultivation or when the color of the medium and the color of microorganisms are similar, detection accuracy of microorganisms may not be sufficiently ensured. In the detection method of Patent Document 2, microorganisms are detected by using color data specified in advance. Therefore, when the color of microorganisms is changed or when the color of a medium and the color of microorganisms are similar, detection accuracy of microorganisms may not be sufficiently ensured.